/*
 * NetBSD: qsort.c,v 1.20 2009/06/01 06:37:40 yamt Exp $
 */

#include <sys/cdefs.h>
#include <sys/types.h>

#include <errno.h>
#include <stdlib.h>

static inline char *med3 __P((char *, char *, char *, int (*)(const void *, const void *)));
static inline void	swapfunc __P((char *, char *, size_t, int));

#define min(a, b)	(a) < (b) ? a : b

/*
 * Qsort routine from Bentley & McIlroy's "Engineering a Sort Function".
 */
#define swapcode(TYPE, parmi, parmj, n) { \
	size_t i = (n) / sizeof (TYPE); 	  \
	TYPE *pi = (TYPE *)(void *)(parmi);   \
	TYPE *pj = (TYPE *)(void *)(parmj);   \
	do { 				 \
		TYPE	t = *pi; \
		*pi++ = *pj;	 \
		*pj++ = t;	     \
	} while (--i > 0);   \
}

#define SWAPINIT(a, es) swaptype = ((char *)a - (char *)0) % sizeof(long) || \
	                               es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;

static inline void swapfunc(char *a, char *b, size_t n, int swaptype)
{

	if (swaptype <= 1)
		swapcode(long, a, b, n)
	else
		swapcode(char, a, b, n)
}

#define swap(a, b) \
	if (swaptype == 0) { \
		long t = *(long *)(void *)(a); \
		*(long *)(void *)(a) = *(long *)(void *)(b); \
		*(long *)(void *)(b) = t; \
	} else \
		swapfunc(a, b, es, swaptype)

#define vecswap(a, b, n) if ((n) > 0) swapfunc((a), (b), (size_t)(n), swaptype)

static inline char *med3(char *a, char *b, char *c, int (*cmp) __P((const void *, const void *)))
{
	return cmp(a, b) < 0 ?
	      (cmp(b, c) < 0 ? b : (cmp(a, c) < 0 ? c : a ))
         :(cmp(b, c) > 0 ? b : (cmp(a, c) < 0 ? a : c ));
}

void qsort(void *a, size_t n, size_t es, int (*cmp) __P((const void *, const void *)))
{
	char *pa, *pb, *pc, *pd, *pl, *pm, *pn;
	size_t d, r;
	int swaptype, cmp_result;

#if 0
	_DIAGASSERT(a != NULL);
	_DIAGASSERT(cmp != NULL);
	
#else
    if ((a == NULL) || (cmp == NULL))
        return;
        
#endif

loop:

	SWAPINIT(a, es);
	if (n < 7)
	{
		for (pm = (char *) a + es; pm < (char *) a + n * es; pm += es)
			for (pl = pm; pl > (char *) a && cmp(pl - es, pl) > 0; pl -= es)
				swap(pl, pl - es);
		return;
	}

	pm = (char *) a + (n / 2) * es;
	if (n > 7)
	{
		pl = (char *) a;
		pn = (char *) a + (n - 1) * es;
		if (n > 40)
		{
			d = (n / 8) * es;
			pl = med3(pl, pl + d, pl + 2 * d, cmp);
			pm = med3(pm - d, pm, pm + d, cmp);
			pn = med3(pn - 2 * d, pn - d, pn, cmp);
		}
		pm = med3(pl, pm, pn, cmp);
	}
	swap(a, pm);
	pa = pb = (char *) a + es;

	pc = pd = (char *) a + (n - 1) * es;
	for (;;)
	{
		while (pb <= pc && (cmp_result = cmp(pb, a)) <= 0)
		{
			if (cmp_result == 0)
			{
				swap(pa, pb);
				pa += es;
			}
			pb += es;
		}

		while (pb <= pc && (cmp_result = cmp(pc, a)) >= 0)
		{
			if (cmp_result == 0) {
				swap(pc, pd);
				pd -= es;
			}
			pc -= es;
		}

		if (pb > pc)
			break;

		swap(pb, pc);
		pb += es;
		pc -= es;
	}

	pn = (char *) a + n * es;
	r = min(pa - (char *) a, pb - pa);
	vecswap(a, pb - r, r);
	r = min((size_t)(pd - pc), pn - pd - es);
	vecswap(pb, pn - r, r);
	if ((r = pb - pa) > es)
		qsort(a, r / es, es, cmp);
	if ((r = pd - pc) > es)
	{
		/* Iterate rather than recurse to save stack space */
		a = pn - r;
		n = r / es;
		goto loop;
	}

	/* qsort(pn - r, r / es, es, cmp); */
}


